Exxon fights $6.7bn payout

A US federal judge has ordered Exxon Mobil Corporation to pay about $US6.75 billion ($A8.8 billion) to thousands of Alaskans affected by the 1989 Exxon Valdez oil spill.

The ruling is the latest of several damage awards in the case over the past decade - the result of successful appeals in the federal court by Exxon. The company plans to appeal again.

Wednesday's ruling by US District Judge Russel Holland ordered the Texas-based company to pay $4.5 billion in punitive damages and an estimated $2.25 billion in interest.

The money is to go to 32,000 fishermen, Alaska natives, landowners, small businesses and cities affected by the 40-million-litre spill in the Prince William Sound.

"We have now closed the trial court doors for the last time in this litigation after 15 years," said David Oesting, lead attorney for the plaintiffs. "We're definitely on track to the end of the entire dispute."

The judge had been ordered by the 9th US Circuit Court of Appeals to reconsider the damages awarded in an earlier ruling in light of a Supreme Court decision last year concerning punitive damages.

"This ruling flies in the face of the guidelines set by the appeals court," company spokesman Tom Cirigliano said.

He said the 9th Circuit has twice vacated Judge Holland's decisions in the case.

Judge Holland reduced the Exxon punitive damages award to $4 billion a year ago after a three-judge panel of the 9th Circuit sent the original $5 billion verdict back, saying it was excessive.

The spill occurred on March 23, 1989, less than three hours after the Exxon Valdez left the Alyeska Pipeline terminal. The ship grounded, rupturing eight of its 11 cargo tanks and spewing some 40.9 million litres of crude oil into the sound.

An estimated 250,000 seabirds and thousands of marine mammals died as a result of the spill, which contaminated more than 1930 kilometres of shoreline.

Lingering effects include declines in various marine populations, as well as stunted growth in species such as pink salmon.